The present invention relates to an improved process for recovering and causing highly viscous petroleum products to flow through drilled well bores or pipelines.
Causing highly viscous petroleum products or residues, in particular those with an API grade lower than 15, to flow through ducts is difficult owing to their high viscosity and consequently poor flowing ability.
A method for improving the flowing ability of, and recovering, these highly viscous products consists in adding lighter crude petroleum grades or hydrocarbons to said products. This blending decreases the viscosity of the system and hence increases the flowing ability thereof, but displays the drawback of requiring considerably high investment costs and consequently is rather expensive. Furthermore, not always light fractions or crude petroleum grades are available.
Another method for improving the fluidity of highly viscous products inside the pipelines, consists in installing heating means at frequent intervals along the pipeline; in that way, the so heated crude or petroleum product has a low viscosity and, therefore, conveying it is easier. These heating means can be operated by using a portion of conveyed product as fuel. This technique may result in the loss of 15-20% of transported product.
Another method for conveying heavy petroleum products or residues through pipelines consists in pumping them through the pipeline as more or less fluid aqueous emulsions. Said emulsions are of oil-in-water (O/W) type and therefore are decidedly more fluid than the crude petroleum to be conveyed.
The oil-in-water emulsions, prepared by adding, with stirring, water and an emulsifier to the oil to be conveyed, are then pumped into the pipeline.
The emulsifier agent should produce a stable and fluid oil-in-water emulsion with a high oil level.
For the process to be advantageous, it is necessary that the emulsifier agent is cheap and capable of generating emulsions which are stable during the pumping period.
The emulsifiers proposed heretofore are not fully compliant with the above said requisites.
For example, U.S. Pat. Nos. 4,246,920, 4,285,356, 4,265,264 and 4,249,554 disclose emulsions which contain an oil level of only 50%; under these conditions, this means that half volume of the pipeline is unavailable for transporting petroleum.
On the other hand, the Canadian patent Nos. 1,108,205; 1,113,529 and 1,117,568, as well as U.S. Pat. No. 4,246,919 disclose rather small decreases in viscosity, notwithstanding the relatively low oil proportion.
U.S. Pat. No. 4,770,199 discloses, on the contrary, emulsifier agents which are constituted by complex blends of non-ionic alkoxylated surfactants with carboxylated ethoxylated-propoxylated species. The non-ionic surfactant contained in the above said blend obviously is sensible to temperature, and consenquently it may become insoluble in water under determined temperature conditions. Furthermore, the above said surfactants are very expensive and contribute to increase the process costs.
Finally, EP-B-237,724 uses, as emulsifier agents, mixtures of carboxylated ethoxylates and sulfate ethoxylates, products not easily available on the market, and rather expensive.